This second stack leads to JNI problems on Android, because ART fetches
the address and size of the original stack using pthread functions
(see GetThreadStack in art/runtime/thread.cc), and (presumably) treats
stack addresses outside of the original stack as invalid. (What I don't
understand is why some JNI operations on the CPU thread work fine
despite this but others don't.)
Instead of creating a second stack, let's borrow the approach ART uses:
Use pthread functions to find out the stack's address and size, then
install guard pages at an appropriate location. This lets us get rid
of a workaround we had in the MsgAlert function.
Because we're no longer choosing the stack size ourselves, I've made some
tweaks to where the put the guard pages. Previously we had a stack of
2 MiB and a safe zone of 512 KiB. We now accept stacks as small as 512 KiB
(used on macOS) and use a safe zone of 256 KiB. I feel like this should
be fine, but haven't done much testing beyond "it seems to work".
By the way, on Windows it was already the case that we didn't create
a second stack... But there was a bug in the implementation!
The code for protecting the stack has to run on the CPU thread, since
it's the CPU thread's stack we want to protect, but it was actually
running on EmuThread. This commit fixes that, since now this bug
matters on other operating systems too.
This very much isn't a build configuration that we're going to ship,
but I want to be able to tell people that they can build it on their
own if they really want to see how terribly it performs :)
Just like before, you'll need to edit two lines in app/build.gradle to
define ENABLE_GENERIC=ON and actually enable armeabi-v7a if you want an
armeabi-v7a build. This commit just fixes some compilations errors that
crop up if you do so.
This fixes a problem I was having where using frame advance with the
debugger open would frequently cause panic alerts about invalid addresses
due to the CPU thread changing MSR.DR while the host thread was trying
to access memory.
To aid in tracking down all the places where we weren't properly locking
the CPU, I've created a new type (in Core.h) that you have to pass as a
reference or pointer to functions that require running as the CPU thread.
While the NV extension is totally fine, the KHR extension should be able to support more hardware.
For NVIDIA, the hardware either supports both or neither, it just needs a driver from the last two years.
For AMD, the drivers from late 2022-12 seems to bring support for the KHR extension.
For Intel, the KHR is also supported for some years.
- Cancel doesn't shut down anymore.
Allowing it to be used multiple times thoughout the life of
the WorkQueue
- Remove Clear, so we only have Cancel semantics
- Add IsCancelling so work items can abort early if cancelling
- Replace m_cancelled and m_thread.joinable() guars with m_shutdown.
- Rename Flush to WaitForCompletion (As it's ambiguous if a function
called flush should be blocking or not)
- Add documentation
